Functional testing instrument for telephone cables - with direct indication of faulty conductor in a quad

摘要

The instrument tests conductors combined to form quads, whereby each conductor in a quad has a corresponding switching element which conducts current if the conductor is faulty, and all four switching elements are connected in series in an indicating instrument lead. A light emitting diode is connected in parallel to each switching element and all the diodes are in series with one another. If a conductor exhibits a fault, the corresponding diode will continue to emit light, whilst the other three diodes will be extinguished.